Wet bulb thermostat control



Jan. 21, 1941. s M ANDERSON 2,229,164

WET BULB THERMOSTAT CONTROL SYSTEM Filed May 3, 1959 SAMUEL M. ANDERSON byu-@m11 J M Patented Jan. 2l, 1941 UNITED STATES WET BULB THERMOSTAT CONTROL SYSTEM Samuel M. Anderson, Sharon, Mass.,vassignor to B. F. Sturtevant Company, Hyde Park, Boston,

Mass.

Application May s, 1939, serial No. 271,611

4 Claims.

It is desirable for eliminating odors, for providing germ free air and for providing the highest quality conditioned air, to use less recirculated air for air conditioning and to use more l outdoor air in the air conditioning of railway passenger cars. In the past, the practice has been to use 25% outdoor air and 75% recirculated air. The use of such large quantities of recirculated air has resulted not only in unpleasant odors but in the recirculation of harmful germs added by the occupants of the passenger space. In addition, no amount of conditioning of recirculated air can provide the tone and quality of outdoor air.

According to this invention all outdoor air is used in an air conditioning system for railway passenger cars, and this is economically accomplished by a novel wet bulb thermostat control system which fits in advantageously with existing car apparatus and which provides 100% outdoor air when the outdoor wet bulb temperatures are within the range in which all outdoor air may be conditioned without too great a load upon the cooling or heating system, and which provides partial recirculation in extreme temperature ranges.

The invention will now be described with reference to the drawing which illustrates diagrammatically one embodiment of the invention applied to a railway passenger car.

The overhead air conditioner 5 may be supplied with a volatile refrigerant from the usual compressor 6 and condenser 1. mostat 8 may control car temperatures in the cooling season by controlling the energizing circuit connecting the motor 9 to the usual axle generator I0' and its associated battery (not shown).

The blower II draws outdoor air through the dampers I2 and recirculated airthrough the dampers I3 and supplied it to the conditioner 5.

The thermostat I5 may be of any well known. wet bulb type having a water wetted wick and responds to changes in the wet bulb temperature of the outdoor air and acts when the wet bulb temperature is below say '10 F. to open the circuit connecting the damper motor I4 to the axle generator I0, to cause the motor I4 to The car ther- I circuit of the motor I4 is closed causing the motor to partially close the dampers I2 and to partially open the dampers I3 for partial recirculation.

'I'he evaporator surface of the thermostat 5 I5 is wetted by water supplied through the valve I6 and tube I1 from the water tank I8. It is preferred that the internal diameter of the tube Il be so constricted that the volume of Water supplied thereby to the thermostat I5 is that 10 which would be expected to be evaporated therein. Compressed air from the source I?, which may be the supply source for the a1r I brakes of the car, supplies air into the tank I8 for building up a sufiicient pressure to force 15 the water through the tube I1 to the overhead thermostat I5. The solenoid 20 opens the valve I6 in the water line when the start-up switch 2l is closed to energize the entire system. A

More refrigeration is required and the equlp- 20 ment is in operation for greater periods of time when the thermostat has acted to supply 100% outdoor air to the system and it is realized that at the low car speeds when the generator I0 is not driven fast enough to charge its battery, the 25 thermostat I5 when the wet bulb temperature is below F. would cause too great a load on the battery and would cause it to become discharged. Accordingly, the relay 22 is provided for shorting out the thermostat I5 at car speeds 30 below the critical one. In a standard air conditioned railway car, a control panel 23 connected to the electric supply equipment, is placed in a corridor in one end of the car, and above, the panelis mounted a green electric light 24 35 which glows when the car is moving below the critical battery charging speed-of 20 miles per hour, and which goes out when the car speed is above 20 miles per hour. The relay 22 is connected in series with this light 22 and is ener- 40 gi'zed to close contacts which are connected to the wires 25 to short out the thermostat I5 and to close the circuits which normally would be closed by the thermostat I5 when the wet bulb A, temperature of the outdoor air was above '70 F.l 45 This causesY the damper motor to .adjust the dampers I2 and I3 for partial recirculation thus reducing the air conditioning load and as a result, the load upon' the electric supply equipment. 50

lWhile one embodiment of the invention has Y been described for the purpose of illustration, it should be understood that the invention is not limited to the exact apparatus and arrangethereof may be suggested by those skilled in the art without departure from the substance of the invention.

What is claimed is: 1. In an air conditioning system for passenger vehicles having a motor driven accessory, a. wet bulb thermostat in control thereof, an electric supply, and apparatus including an electric switch for closing a circuit including said supy ply, said wet bulb thermostat and the motor for said accessory, a water tank, a conduit connecting said tank with said wet bulb thermostat. a compressed air source connected to said tank for forcing water through said conduit to said thermostat, and means'fon initiating the supply* said means for increasing the proportion of outdoor air when its wet bulb temperature is below a predetermined point, and means responsive to vehicle speeds for rendering said thermostat ineffective when the speed falls Vbelow a predetermined speed.

3. An air conditioning system for a. vehicle, comprising an air cooler, mean's for supplying outdoor and recirculated air into said cooler, an outdoor wet bulb thermostat for adjusting said means for increasing the proportion of outdoor air when its wet bulb` temperature is below a predetermined point, and means responsive to vehicle speeds for rendering said thermostat ineffective and for adjusting said rst mentioned means for decreasing the proportion of outdoor air when the speed falls below a predetermined speed.

4. An air conditioning system for a vehicle, comprising an air cooler, means for supplying outdoor and recirculated air into said cooler, and means responsive to outdoor wet bulb temperatures and to" vehicle speeds for adjusting said first mentioned means for increasing the proportion of outdoor air when the outdoor wetbulb temperature is below a predetermined temperature and the speed is above a predetermined speed and for decreasing the proportion of outdoor air when the outdoor Wet bulb temperature `is above1 saidwpredetermined.,temperature or'the speed is below said predetermined speed.

SAMUEL M. ANDERSON. 

